Just an idle thought, but, does that classic lyric refer to hemlines? It's been a funny old summer in the UK, cool and very damp, but the sun's been out for a few days now and it's looking much better. However, compare and contrast:

Summer temperatures rarely go above 30 °C. The record maximum is 38.5 °C (101 °F) recorded in Kent, in August 2003 - Wikipedia: Climate of the British Isles

According to Whitstable Windsurfing the temperature has exceeded 40 °C on a number of days this August; is their thermometer sitting in the sun?